Factors influencing the clinical performance of dental x-ray systems including a portable dental fluoroscope are being evaluated in vitro using computer simulations and quantitative measurements derived from radiographic phantoms. Measures of clinical utility based on an endodontic task using dentulous skulls are being determined for various film/screen combinations in order to access the minimum information capacity required. It is anticipated that these findings will aid in establishing the minimum signal-to-noise ratio and resolution characteristics necessary for endodontic radiography. Other studies based on spectral analyses of 125I and 153Gd using a non-linear systems model indicate significant technical limitations which minimize the practicality of such isotopes as x-ray sources in routine dental fluoroscopic applications. Factors influencing geometric registration of successive radiographic projections are also being explored in an effort to establish a practical means for quantitatively tracing degenerative changes in tissues of dental interest over time.